arXiv subjects

Sofia Wechsler

Publications and source records attributed to Sofia Wechsler.

At least 19 recordsLinked to original sources

arXiv2023

What in fact proves the violation of the Bell-type inequalities?

A. Peres constructed an example of particles entangled in the state of spin singlet. He claimed to have obtained the CHSH inequality and concluded that the violation of this inequality shows that in a measurement in which some variables are tested, other variables, not tested, have no defined value. In the present paper is proved that the correct conclusion of the violation of the CHSH inequality is different. It is proved that the classical calculus of probabilities of test results, obeying the Kolmogorov axioms, is unfit for the quantum formalism, dominated by probability amplitudes.

quant-ph↗

arXiv2022

The Wave Function Cannot be a Real Wave Then Can We Speak of an Ontology of Particles

Is the wave function a physical reality traveling through our apparatus? Is it a real wave, or it is only a mathematical tool for calculating probabilities of results of measurements? Different interpretations of the quantum mechanics (QM) assume different answers to this question. It is shown in this article that the assumption that the wave function is a real wave entails a contradiction with the predictions of the QM, when the special relativity is invoked. Therefore, this text concentrates on interpretations which conjecture that the reality that moves in our apparatuses is particles, and they move under the constraints of the wave function. The de Broglie Bohm interpretation, which matches this picture, assumes that the particle travels along a continuous trajectory. However, the idea of continuous trajectories was proved to lead to a contradiction with the quantum predictions. Therefore this interpretation is not considered here. S. Gao conjectured that the particle is in a permanent random and discontinuous motion (RDM). As it jumps all the time from place to place, the total set of occupied positions at a certain time is given by the absolute square of the wave function. As motivation for his idea, Gao argued that if a charged particle were simultaneously in two or more locations at the same time, the copies of the particle would repel one another, destroying the wave function. It is proved here that the quantum formalism renders this motivation wrong. Although refuting this motivation, the RDM interpretation is examined here. A couple of problems of this interpretation are examined and it is proved that they do not lead to any observable contradictions with the QM predictions, except one problem which seems to have no solution. In all, it appears that none of the wide-spread interpretations of the QM is free of contradictions.

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arXiv2022

A Non Relativistic Argument Against Continuous Trajectories of Particles

A thought experiment is described and the probability of a particular type of results is predicted according to the quantum formalism. Then, the assumption is made that there exists a particle that travels from the source to one of the detectors, along a continuous trajectory. A contradiction appears: for agreeing with the quantum prediction, the particle has to land at once on two space separated detectors. Therefore, the trajectory of the particle, if it exists, cannot be continuous.

physics.gen-ph↗

arXiv2021

What was in the apparatus before the click

When a quantum system is described by a wave function consisting in a couple of wave-packets, each wave packet traveling on a separate path, a commonly asked question is why at a given time only one of the wave packets is able to trigger a click in a detector. In the second half of the last century many scientists considered the possibility that not all these wave-packets are identical. Namely, that there exist full waves and empty waves. The two types of waves were supposed to be identical in all the experiments, e.g. able to produce interference when meeting, however, the full wave was supposed to be able to trigger a detector, while the empty wave was supposed to leave the detector silent. The present text describes an experiment which, for explaining the results, seems to beg the hypothesis of full and empty waves.

quant-ph↗

arXiv2021

What is realism and how can it be non-local?

The concept of realism in quantum mechanics means that results of measurement are caused by physical variables, hidden or observable. Local hidden variables were proved unable to explain results of measurements on entangled particles tested far away from one another. Then, some physicists embraced the idea of nonlocal hidden variables. The present article proves that this idea is problematic, that it runs into an impasse vis-à-vis the special relativity.

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arXiv2021

About the Nature of the Quantum System, an Examination of the Random Discontinuous Motion Interpretation of the Quantum Mechanics

What is the quantum system? Consider the wavefunction of the electron, what we call single particle wave-function and assume that it contains N wave packets. If we pass all the wave packets through an electric field, all are deflected, as if each one of them contains an electron. However, if we bring any two wave packets to travel close to one another, they do not repel one another, as if at least one of them contains no charge. In trying to solve the measurement problem of the quantum mechanics (QM), different interpretations were proposed, each one coming with a particular ontology. However, only one interpretation paid explicit attention to the contradiction mentioned above. This interpretation was proposed by S. Gao who named it random discontinuous motion (RDM), because it assumes the existence of a particle that jumps from place to place at random. The particle carries all the physical properties of the respective type of particle, mass, charge, magnetic momentum, etc. It jumps under the control of a so called instantaneous condition about which Gao did not give details so far. Along with presenting problems of the QM that this interpretation solves, this text reveals difficulties vis-à-vis entanglements and the special relativity.

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arXiv2020

Does a measurement really collapse the wave function?

A single-particle multi-branched wave-function is studied. Usual which-path tests show that if the detector placed on one branch clicks, the detectors on the other branches remain silent. By the collapse postulate, after this click, the state of the particle is reduced to a single branch, the branch on which the detector clicked. The present article challenges the collapse postulate, claiming that when one branch of the wave-function produces a click in a detector, the other branches don't disappear. They can't produce clicks in detectors, but they are still there. An experiment different from which-path test is proposed, which shows that detectors are responsible for strongly decohering the wave-function, but not for making parts of it disappear. Moreover, one of the branches supposed to disappear may produce an interference pattern with a wave-packet of another particle.

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arXiv2019

Are superluminal "signals" an acceptable hypothesis? - Difficulties in building a communication protocol with them

The local hidden variable assumption was repeatedly proved unable to explain results of experiments in which contextuality is involved. Then, the correlated results of measurements of entangled particles, began to be attributed to a communication between particles through so-called "signals". These "signals" need to possess superluminal velocity or move backward in time. No object that has a rest-mass, not even the photons whose rest mass is zero, behave this way. Still, as the nature of the presumed "sinals" is not known, people don't reject the idea, despite the conflict with the theory of relativity. For this reason, the present article examines the "signals" from another point of view: wherever runs a communication, there has also to exist a communication protocol. The article tries to outline a communication protocol between the space-separated, entangled particles, and comes to a contradiction, making the idea of such a communication highly doubtable.

quant-ph↗

arXiv2019

What particles that never met "know" of one another?

An experiment proposed by Yurke and Stoler, and similar to that realized experimentally by Sciarrino et al., is analyzed. In Sciarrino's realization, identical photons from a degenerated down-conversion pair are used, i.e. the photons met in the past. In the experiment analyzed here the particles are also identical, but from different sources. As long as one can tell from which source came each particle, the joint wave function remains factorizable. However, a configuration is created in which one cannot tell anymore which particle came from which source. As a result, the wave function becomes non-factorizable, symmetrical (for bosons) or antisymmetrical (for fermions). In part of the cases the situation is even more surprising: the particles never meet, s.t. the symmetry (antisymmetry) is produced at-a-distance without the particles having had the possibility to interact in any way.

quant-ph↗

arXiv2019

Do entanglements need some superluminal hidden connection?

Local hidden variables theories didn't succeed to explain the correlations revealed by entanglements. It is obvious that the explanation of the correlations stands in non-local effects, but nobody has ever detected any carriers that travel with superluminal velocity s.t. they could candidate for some superluminal connection between distant particles, in order to adjust the results to the correlations. This text explains that the role of creating the correlations is played by what is called here the "Negative". This is the part that was removed from the wave function of the independent particles, in order to obtain the entanglement. As it is shown here, for du-particle experiments the Negative consists in du-particle wave-packets. They enter both regions where the particles are tested, s.t. the Negative "knows" the response given by one particle, and erases the possibilities of forbidden responses from the other particle.

quant-ph↗

arXiv2019

Action at a distance and the no-mediator theorem

It is known that outcomes of space-like separated measurements of entangled particles are interdependent. As in the classical physics no one saw action-at-a-distance, not mediated by some real communication using a carrier, people look for some mediator that makes possible an influence-passing between the distant particles. The wave function does not comprise such a kind of object. The present text tries to incorporate the mediator in the formalism of the quantum mechanics. The result is a contradiction.

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arXiv2019

Nonlocality of single fermions - branches that borrow particles

An experiment performed in 2002 by Sciarrino et al. provided a simple proof of the nonlocality of a single photon whose wave function is multi-branched. The difference between this experiment and others similar, is that the tester-particle used by Sciarrino to "feel" this nonlocality is another photon identical to the tested one. Such an experiment be can in principle performed with fermions too, and this is the case ivestigated in this article. The novel phenomenon revealed by Sciarrino's experiment, is the particle "borrowing". If a single particle is described by a two-branched wave function, then only one of these branches produces a detection at a time, the other ranch remains "silent". What happens in this experiment is that the silent branch "borrows" a particle from another source, if available in the neighborhood, and also produces a detection. To illustrate this feature more obviously, a modificaton of Sciarrino's experiment is proposed. Two sources of particles are made available in the neighborhood of the two branches. What then happens is that each branch takes and populates itself with a particle from whichever source is at hand.

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arXiv2015

A problem with Bell-type Inequalities, the origin of the quantum non-locality, and a full/empty waves model for entanglements

Whether the quantum mechanics (QM) is non-local is an issue disputed for a long time. The violation of the Bell-type inequalities was considered as proving this non-locality. However, these inequalities are constructed on a class of local hidden variables, which obey the calculus with positive probabilities. Such a calculus is rather suitable for billiard balls while the QM deals with wave-packets of complex amplitudes. There is no wonder that a calculus with positive numbers does not match a calculus with complex numbers. The present text describes a different model of hidden variables for entanglements, model that reproduces the quantum predictions in different experiments, and also explains why the QM is nonlocal. The model deals with waves, some of them full and the others empty, and the hidden variables mark which waves are full. The basic physical concept with which the model operates is joint amplitudes of probability, and not probabilities. The latter are a secondary concept, the probability of a combination of results being equal to the absolute square of sum of all the contributing joint amplitudes. Thus the non-locality appears: a) a joint amplitude ignores distance, it handles distant particles as if they were one single particle at one single place, b) joint amplitudes are complex numbers and the sum of several contributions may vanish, blocking the respective combination of wave-packets and therefore of results. Although showing the success of the model, this text does not advocate for full/empty waves. It is shown that this hypothesis works only as long as one does not consider moving observers, and does not compare their conclusions. The real purpose here is to point to a severe impasse: assuming the existence of a preferred frame contradicts the theory of relativity, while refuting the full/empty waves idea one runs into other insurmountable difficulties.

physics.gen-ph↗

arXiv2010

About empty waves, their effect, and the quantum theory

When a quantum object -- a particle as we call it in a non-rigorous way -- is described by a multi-branched wave- function, with the corresponding wave-packets occupying separated regions of the time-space, a frequently asked question is whether the quantum object is actually contained in only one of these wave-packets. If the answer is positive, then the other wave-packets are called in literature empty waves. The wave-packet containing the object is called a full wave, and is the only one that would produce a recording in a detector. A question immediately arising is whether the empty waves may also have an observable effect. Different works were dedicated to the elucidation of this question. None of them proved that the hypothesis of full/empty waves is correct - it may be that the Nature is indeed non-deterministic and the quantum object is not confined to one region of the space-time. All the works that proved that the empty waves have an effect, in fact, proved that if there exist full and empty waves, then the latter may have an observable effect. This is also the purpose and the limitation of the present work. What is shown here is that if the hypothesis is true, the empty waves have an influence. An experiment is indicated which reveals this influence. The analysis of the experiment is according to the quantum formalism. This experiment has the advantage of being more intuitive and practically more feasible than a previous proposal also in agreement with the quantum formalism. However, the presently proposed experiment also shows that the quantum theory is not in favor of the above hypothesis.

quant-ph↗

arXiv2009

The basic Leggett inequalities don't contradict the quantum theory, neither the classical physics

The basic Leggett inequalities, i.e. those inequalities in which the particular assumptions of Leggett's hidden-variable model (e.g. Malus law) were not yet introduced, are usually derived using hidden-variable distributions of probabilities (although in some cases completely general, positive probabilities would lead to the same result). This fact creates sometimes the illusion that these basic inequalities are a belonging of the hidden-variable theories and are bound to contradict the quantum theory. In the present text the basic Leggett inequalities are derived in the most general way, i.e. no assumption is made that the distribution of probabilities would result from some wave function, or from some set of classical variables. The consequence is that as long as one and the same probability distribution is used in the calculus of all the averages appearing in the basic Leggett inequalities, no contradiction may occur. These inequalities may be violated only when different averages are calculated with different distributions, for example, some of them calculated with the quantum formalism and the others with some distribution of classical parameters.

quant-ph↗

arXiv2009

A counter-argument to "Hidden variable models for quantum theory cannot have any local part" arXiv:0801.2218

Colbeck and Renner [arXiv:0801.2218] analyzed a class of combined models for entanglements in which local and non-local hidden variables cooperate for producing the measurement results. They came to the conclusion that the measurement results are fully independent of the local components of the hidden variables. Their conclusion is based mainly on an assumption on the local hidden variables, assumption similar to the non-signaling property of probabilities of observables' values. In the present text it is proved that hidden variables are not observables, so their distributions of probabilities do not necessarily possess the non-signaling property. Also, a counter-example is brought to the Colbeck and Renner assumption, showing that their type of models and conclusion are not general. The question whether hidden variables, local or non-local, exist or not, remains open.

quant-ph↗

arXiv2009

Hidden variable models for entanglements can or cannot have a local component?

A recent article of Colbeck and Renner tackled the problem whether entanglements may be explained by combined models of local and non-local hidden variables. To the difference from previous works they considered models in which each pair of entangled particles behaves in the same way, and the particles in the pair are equivalent, i.e. each of them produces its response to a measurement according to both local and non-local hidden variables. Their article aimed at proving that the local hidden variable component in such models has no effect on the measurement results, i.e. only the non-local variables are relevant. However, their proof deals with a very restrictive case and assumes questionable constraints on the hidden variables. The present text studies the Colbeck and Renner class of models on a less restrictive case and under no constraints on the hidden variables. It is shown again that the local component cannot have any influence on the results. However, the Colbeck and Renner class of models is not the only one possible. A different class is described, and it admits local hidden variables by the side of the non-local influence. This class presents a couple of advantages.

quant-ph↗

arXiv2009

Where was the particle?

The hypothesis of empty/full waves considers that a click in a detector is triggered by a property carried by the wave-packet that impinges on that detector. Different authors call this property particle, but according to the terminology of this hypothesis, the term full wave is used in this text. The present article discusses the validity of the empty/full waves hypothesis. It is shown that the energy conservation principle imposes for a full wave a continuous trajectory from the source to the detector. That gives legitimacy to the question -- in case the wave function consists in a couple of space-separated branches -- which wave-packet was a full wave before the click in the detector, or, in other authors' terminology, where was the particle before the detector clicked. This question is a counterfactual question. In some multi-particle experiments, e.g. Hardy's thought-experiment with an electron and a positron, the combination of the empty/full waves hypothesis and counterfactual reasoning leads to a contradiction with the predictions of the quantum theory. However, it is shown here that this contradiction is solvable if the locality requirement is relaxed. To the difference from the local hidden variables, it is not possible to prove or disprove the idea of empty/ full waves, at least at present. But it is possible to ask whether this hypothesis offers a solution to the quantum puzzles. The answer is negative. For instance it offers no solution to the before-before loop. The question remains open whether the empty/full waves hypothesis is correct, or "God plays dice".

quant-ph↗